1. Field of the Invention
The present invention relates to image sensing device, and in particular to a contact image sensing device.
2. Description of Related Art
Contact image sensor is one of linear image sensors, and is applied to scanner, fax machine, and multi function business machine, plane images or documents are scanned into the contact image sensor and then converted to electronic form for convenience of storage, display, or transmission.
The operating principle of the contact image sensor is projecting light generated from a light source thereof to the image or document, and converging reflected light reflected by the image or document on photosensitive component, such as charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) by a lens assembly. The photosensitive component then converts optical signal (the reflected light) into electronic signal and generates analog or digital pixel data.
Reference is made to FIG. 1, which is a sectional view of a conventional contact image sensor. The contact image sensor 1 includes a housing 10, a light emitting component 12, a rod lens assembly 14, and a sensing unit 16. The housing 10 forms an accommodating groove 100 and a through groove 102. The light emitting component 12 is arranged within the accommodating groove 100 and used for providing light to illuminant an object (not shown). The rod lens assembly 14 is arranged within the through groove 102. The sensing unit 16 includes a circuit board 160 and a plurality of sensing components 162 placed on the circuit board 160 and electrically connected thereto. The light emitted from the light emitting component 12 and transmitted to the object is reflected by the object and images on the sensing unit 16 via the rod lens assembly 14.
However, the dimension of the rod lens assembly 14 is fixed, and when the rod lens assembly 14 is assembled with in the housing 10, a top end of the rod lens assembly 14 will expose out of the housing 10 such that a surface of the top end of the rod lens assembly 14 for light entering will be scratched by impact or friction and imaging quality of the contact image sensor is then influenced.